This invention relates generally to restorative dentistry and more particularly to dental implant systems. A common type of dental implant system comprises a generally cylindrical body made of biocompatible material and is formed with an outer surface configuration selected to promote osseointegration. For example, a plurality of fins which extend radially outwardly from the side wall of the body or an external thread formed in the side wall. A bore extends through a crestal end of the body along the longitudinal axis of the cylindrical body with at least a portion of the bore having an internal thread adapted to threadingly receive a variety of threaded copings, screws or other threaded posts of a dental prosthesis system.
One of the difficulties in using a threaded member to attach a prosthesis to the implant is the need for tight and lasting engagement of any threaded member received in the bore as well as the need for attaining a selected angular orientation, that is, the tooth simulating prosthesis must be positioned in a precise, given angular orientation. Any looseness between the components can eventually result in breakage due to the lateral forces placed on the components during chewing.
Another type of dental implant system has a smooth circular bore formed with a locking taper for reception of a post of an abutment having a matching locking taper. A system of this type is described and claimed in U.S. Pat. No. 4,738,623, the subject matter of which is incorporated herein by this reference. This type of system has several inherent, distinct advantages over the threaded system described above including the ability to precisely position an abutment in any selected angular orientation and, once tapped into locking engagement, characterized in having complete absence of motion between the implant and the abutment member. This results in fewer implant failures. Yet another advantage of a locking taper system is that a locking taper connection forms a bacterial seal as opposed to a threaded system which inherently has a space between the male and female threads which can be accessed by bacteria. Thus the locking taper system results in better soft tissue health in tissue proximate to the implant site.
It would be desirable, particularly in situations where a user of a threaded system who has had problems with implant failures involving breakage of the abutment member, to be able to convert from a threaded system to a locking taper system however, using presently available procedures and components, this requires removal of the threaded implant and replacement with a locking taper implant with a concomitant healing period of some months.